Retroviruses have long been associated with neoplastic disease in avian and mammalian species. The discovery of infectious human retroviruses which are associated with malignancies has spawned a surge of interest in these agents. Recent work linking a retrovirus, Human Immunodeficiency Virus (HIV), as an etiologic agent of Acquired-Immune Deficiency Syndrome (AIDS) (Gallo, R. C. (1987) Sci. Amer., 256, 47-56) has further intensified this interest.
Research on antiviral agents has progressed far in the past decade in response to the need to treat infections of HIV. The majority of the work on antiretrovirals has focused on the use of nucleoside derivatives as inhibitors of the retroviral reverse transcriptase (Fischl, M. A., et al., N. Eng. J. Med., 317, 185-191 (1987);J. E. Dahlberg, H. Mitsuya, S. B. Blum, S. Broder and S. A. Aaronson, Proc. Natl. Acad. Sci., 84, 2469-2473 (1987); S. Broder, in "Human Retroviruses, Cancer, and AIDS", D. Bolognes; ed., Alan R. Liss, Inc., NY, 1988, pp. 365-380; M. S. Hirsh and J. C. Kaplan, Antimic Agents and Chemotherapy, 31, 839-843 (1987). Many of these agents have characteristics which restrict their clinical utility (D. D. Richman, et al., N. Eng. J. Med., 317, 192-197 (1987); Terasaki, T., Pardridge, W. M., J. Infect. Disease, 158, 630-632 (1988)).
Viral proteases are one of the enzymes which are essential components of virion assembly (J. Wellink and A. Van Kammen, Arch. Virol., 98, 1-26 (1988)). Site specific mutagenesis of the presumed active site of retroviral proteases has demonstrated that active enzyme is necessary for the production of mature, infectious virus particles (I. Katoh, et al, Virology, 145, 280-292 (1985); N. E. Kohl, et al. Proc. Natl. Acad. Sci., 85, 4686-4690 (1988); S. Seelmeier, H. Schmidt, V. Tura, and K. von der Helm, Proc. Natl. Acad. Sci., 85, 6612-6616 (1988)). Consequently, interference of proteolytic processing through the use of enzyme inhibitors is an attractive chemotherapeutic target for the treatment of viral diseases. Expression of HIV protease in E. coli (S. Seelmeier, H. Schmidt, V. Tura, and K. von der Helm, Proc. Natl. Acad. Sci., 85, 6612-6616 (1988); M. C. Graves, J. J. Lim, E. P. Heimer and R. A. Kramer, Proc. Natl. Acad. Sci., 85, 2449-2453 (1988); C. DeBouck, et al., Proc. Natl. Acad. Sci., 84, 8903-8906 (1987); J. Mous, E. P. Heimer and S. F. J. Le Grice, J. Virol., 62, 1433-1436 (1988)), and chemical synthesis (T. D. Copeland and S. Oroszlan, Gene Anal. Tech., 5, 109-115 (1988); J. Schneider and S. B. H. Kent, Cell, 54, 363-368 (1988); R. F. Nutt, et al, Proc. Natl. Acad. Sci., 85, 7129-7133 (1988)) of active enzyme have provided in vitro systems to facilitate the study of this protein.
The antifungal antibiotic cerulenin, 4-Oxo-2R,3S-epoxy-trans,trans-2,5-dodecadienyl amide has been reported to exhibit antiretroviral activity against Rous Sarcoma Virus (H. Goldfine, J. B. Harley and J. A. Wyke, Biochem. Biophys. Acad., 512, 229-240 (1978)) and Murine Leukemia Virus (I. Katoh, Y. Yoshinaka and R. B. Luftig, Virus Res., 5, 265-276 (1986)) in vitro. Originally studied for its inhibition of fatty acid synthesis through the inhibition of .beta.-ketoacetyl transferase, (for review, see S. Omura, Bacteriological Rev., 40, 681-697 (1976)) cerulenin apparently interferes with polypeptide processing during virus particle assembly (K. Ikuta and R. B. Luftig, Virology, 154, 195-206 (1986)). It has been uncertain at what stage of processing the inhibition was occurring, but interference with enzyme catalyzed proteolytic cleavage of virus precursor polypeptides has been assumed to be likely. Cerulenin has also been recently reported to inhibit viral polyprotein processing in HIV infected cells (Pal, R., et al (1988), Proc. Natl. Acad. Sci., 85, 9283-9286). Since cerulenin is a potent inhibitor of fatty acid synthesis, it exhibits a relatively high toxicity (Matsumae, J. Antibiotic., 17a, 1 (1964); Pal, R. et al (1988)). The present invention has been discovered with the above background and disadvantages in mind.